> 
> So let's say consensus is reached on 1 ppm, or maybe 10 ppm or 0.1 ppm.  What 
> is this tolerance measured against?  Right!  Time-of-day = mean solar time.  
> What is "LOD" in all those plots?  Requirements describe the problem space.  
> Mean solar time is a requirement.  1 ppm would be a specification against a 
> proposed solution suitable for evaluation by a trade-off, risks, costs, 
> schedule, sensitivity analyses, etc.

So why aren't all those exotic investigations necessary when countries change 
timezones, which happens with monotonous regularity?    In this case, no-one is 
proposing to change the SI second, rather just to use it as monotonic counter.  
  We've already established that the link between civil time and solar time has 
an uncertainty measured in multiple minutes, and we've already established that 
one-hour steps in civil time are trivial to implement, because they happen 
twice a year.  All we're left with is a vague need to keep the sun roughly 
overhead at noon (although there are few riots in Brest, France, which in the 
summer is about 2hr10 unhitched from solar time) which we can manage with 
daylight saving time type adjustments.     The rest is just "sky is falling" 
stuff,.

ian
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